For producing power semiconductor modules, substrates which have an electrically insulating layer, for example of ceramic, that is provided with a metallization layer are often used as circuit carriers. The metallization layer serves for the mounting and interconnection of electrical components. In order to connect electrical leads or other conductors in an electrically conducting manner to the metallization layer, ultrasonic welding methods are often used. This involves the conductor being pressed against the metallization layer by a sonotrode and set in vibration in relation to the metallization layer by means of ultrasound. The relative movement of the two parts to be welded in combination with a pressing force that is acting leads to the formation of an electrically conducting connection that is very secure and stable under changing temperatures.
However, on account of the high pressing force required, there is the risk of the insulating layer being damaged and loosing its insulating resistance. This problem increases as the cross section of the conductor to be welded on increases, because larger cross sections of the conductor require higher pressing forces. Since the insulating layer must not be damaged, the process parameters in the ultrasonic welding must often be chosen outside the range of parameters that is desirable for an optimum ultrasonic welding result.